Ocean Turbulent Mixing in Northern Bohai Strait, China

2013 ◽  
Author(s):  
Shu-xiu Liang ◽  
Zhao-chen Sun ◽  
Song-lin Han ◽  
Hong-qiang Yin ◽  
Bo Bai
Keyword(s):  
Turbulent Mixing ◽  
Yellow Sea ◽  
Dissipation Rate ◽  
Bohai Sea ◽  
Heat Dissipation ◽  
Strong Mixing ◽  
Observation Data ◽  
Diffusivity Coefficient ◽  
Division Line ◽  
Bohai Strait

The measurements of ocean microstructure through which ocean internal mixing mechanism is revealed are taken more often recently. Free-falling turbulence microstructure profiler TurboMAP-9 is used to take a field observation on the area of northern Bohai Strait. 13 stations distributed in Bohai Sea, Yellow Sea and the “division line” between them are measured. Turbulent mixing characteristics of northern Bohai Strait for different seasons are described by analyzing the observation data of ocean turbulence microstructure profile. The results show that the northern Bohai Strait is a strong mixing area during non-stratification period. Turbulent energy dissipation rate ε of winter is bigger than that of autumn and it is strongest near the bottom layers which is in the order of 10−5W/kg. Heat dissipation rate χθ is in the same order of 10−6–10−5°C2/s in autumn as ε and 2–3 orders smaller than ε in winter. Thermal diffusivity coefficient kθ is a little bigger than turbulent mixing rate kρ in autumn and 1–2 orders smaller than kρ in winter. Both the kρ and kθ along the “division line” of Bohai Sea and Yellow Sea are bigger than that of the Bohai Sea and Yellow Sea. Base on the measured data and the analysis, heat dissipation rate and thermal dispersion coefficient can change 2–3 orders in non-stratification seasons which should be paid much attention to, especially for ocean model parameterization and pollutant discharge modeling.

Observations of Turbulent Mixing During a Nonstratification Period in the Yellow Sea

2021 ◽  
Vol 55 (2) ◽  
pp. 185-197
Author(s):  
Yunli Nie ◽  
Xin Luan ◽  
Hua Yang ◽  
Xu Chen ◽  
Dalei Song ◽  
...  
Keyword(s):  
Water Column ◽  
Turbulent Mixing ◽  
Yellow Sea ◽  
Dissipation Rate ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
The Yellow Sea ◽  
Distribution Model ◽  
Entire Water Column ◽  
Diapycnal Diffusivity

Abstract Microstructure profiling measurements collected at the continental shelf of the Yellow Sea (35°38'N, 121°20'E) from December 4 to 5, 2019, were analyzed by focusing on the characteristics of turbulent mixing in the Yellow Sea and its associated influencing factors. The vertical thermohaline structure of the water column was nonstratified during the observation period, resulting in the vertically and temporally consistent distribution of turbulence dissipation and diapycnal diffusivity. The average (in time and space) dissipation rate and diapycnal diffusivity were 2.95 × 10−8 W kg−1 and 1.86 × 10−4 m2 s−1, respectively. In the vertical distribution, intense mixing occurred near the sea surface and within the bottom layers. The temporal variation in dissipation exhibits a diurnal variation that was strongly affected by surface buoyancy flux and wind energy, and a high amount of dissipation was observed at night, with an average dissipation rate of 2.45 × 10−8 W kg−1, which was almost one order of magnitude higher than that in the daytime (3.55 × 10−9 W kg−1). The cumulative distribution functions of the dissipation rate and diapycnal diffusivity across the entire water column during the measurement period could be parameterized by a lognormal distribution model. Further analysis shows that the dissipation rate was positively related to wind speed and rotational barotropic tidal velocity. Compared with the rotating tidal current, wind-driven turbulence was able to penetrate the surface, thereby causing layer mixing throughout the entire water column (R = 0.71), and is a dominant driver of elevated turbulent mixing during wintertime.

scholarly journals A Remote-Sensing Method to Estimate Bulk Refractive Index of Suspended Particles from GOCI Satellite Measurements over Bohai Sea and Yellow Sea

2019 ◽  
Vol 10 (1) ◽  
pp. 23
Author(s):  
Deyong Sun ◽  
Zunbin Ling ◽  
Shengqiang Wang ◽  
Zhongfeng Qiu ◽  
Yu Huan ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Refractive Index ◽  
Spatial Distribution ◽  
Yellow Sea ◽  
Bohai Sea ◽  
Suspended Particles ◽  
In Situ Observation ◽  
Observation Data ◽  
Estimation Model

The bulk refractive index (np) of suspended particles, an apparent measure of particulate refraction capability and yet an essential element of particulate compositions and optical properties, is a critical indicator that helps understand many biogeochemical processes and ecosystems in marine waters. Remote estimation of np remains a very challenging task. Here, a multiple-step hybrid model is developed to estimate the np in the Bohai Sea (BS) and Yellow Sea (YS) through obtaining two key intermediate parameters (i.e., particulate backscattering ratio, Bp, and particle size distribution (PSD) slope, j) from remote-sensing reflectance, Rrs(λ). The in situ observed datasets available to us were collected from four cruise surveys during a period from 2014 to 2017 in the BS and YS, covering beam attenuation (cp), scattering (bp), and backscattering (bbp) coefficients, total suspended matter (TSM) concentrations, and Rrs(λ). Based on those in situ observation data, two retrieval algorithms for TSM and bbp were firstly established from Rrs(λ), and then close empirical relationships between cp and bp with TSM could be constructed to determine the Bp and j parameters. The series of steps for the np estimation model proposed in this study can be summarized as follows: Rrs (λ) → TSM and bbp, TSM → bp → cp → j, bbp and bp → Bp, and j and Bp → np. This method shows a high degree of fit (R2 = 0.85) between the measured and modeled np by validation, with low predictive errors (such as a mean relative error, MRE, of 2.55%), while satellite-derived results also reveal good performance (R2 = 0.95, MRE = 2.32%). A spatial distribution pattern of np in January 2017 derived from GOCI (Geostationary Ocean Color Imager) data agrees well with those in situ observations. This also verifies the satisfactory performance of our developed np estimation model. Applying this model to GOCI data for one year (from December 2014 to November 2015), we document the np spatial distribution patterns at different time scales (such as monthly, seasonal, and annual scales) for the first time in the study areas. While the applicability of our developed method to other water areas is unknown, our findings in the current study demonstrate that the method presented here can serve as a proof-of-concept template to remotely estimate np in other coastal optically complex water bodies.

scholarly journals Multi-Year Winter Variations in Suspended Sediment Flux through the Bohai Strait

2020 ◽  
Vol 12 (24) ◽  
pp. 4066
Author(s):  
Xingmin Liu ◽  
Lulu Qiao ◽  
Yi Zhong ◽  
Wenjing Xue ◽  
Peng Liu
Keyword(s):  
Suspended Sediment ◽  
Yellow Sea ◽  
Bohai Sea ◽  
Sediment Flux ◽  
The Yellow Sea ◽  
The Bohai Sea ◽  
Input Flux ◽  
Suspended Sediment Flux ◽  
Net Flux ◽  
Bohai Strait

The Bohai Strait is the only channel that allows material exchanges between the Bohai Sea and the Yellow Sea. It is also the only channel for the transportation of materials from the Yellow River to the Yellow Sea and the East China Sea. The supply of suspended sediment from the Bohai Sea plays a decisive role in the evolution of the mud area in the northern Yellow Sea and even the muddy area in the southern Yellow Sea. Previous studies have demonstrated that sediment exchange through the Bohai Strait occurs mainly in winter, but due to the lack of long-term observational data, changes in the sediment flux over multiple years have not been studied. In this paper, based on L1B data from the MODIS (Moderate Resolution Imaging Spectroradiometer) -Aqua satellite, an interannual time series of the suspended sediment concentration (SSC) at each depth layers in the Bohai Strait in winter was established through 16 cruises that benefited from the complete vertical mixing water in the strait in winter. The numerical model FVCOM, (Finite-Volume Community Ocean Model) which is forced by the hourly averaged wind field, reflected the effect of winter gales. With the model simulated winter current from 2002 to the present and the SSC at each layer, multi-year winter suspended sediment flux data were obtained for the Bohai Strait. This study found that in the winter, the suspended sediment output from the Bohai Sea to the Yellow Sea through the southern part of the Bohai Strait, while the suspended sediment input from the Yellow Sea to the Bohai Sea is through the northern part. In terms of long-term changes, the net flux ranged between 1.22 to 2.70 million tons in winter and showed a weak downward trend. The output flux and input flux both showed an upward trend, but the increase rate of the input flux was 51,100 tons/year, which was higher than the increase of the output flux rate (46,100 tons/year). These changes were mainly controlled by the increasing strength of east component of winter wind. And the weak decrease in net flux is controlled by the difference of output and input flux.

scholarly journals Nitric oxide (NO) in the Bohai Sea and the Yellow Sea

2019 ◽  
Vol 16 (22) ◽  
pp. 4485-4496 ◽  
Author(s):  
Ye Tian ◽  
Chao Xue ◽  
Chun-Ying Liu ◽  
Gui-Peng Yang ◽  
Pei-Feng Li ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Surface Layer ◽  
Yellow Sea ◽  
Bohai Sea ◽  
Limit Of Detection ◽  
Bottom Layer ◽  
The Yellow Sea ◽  
The Bohai Sea ◽  
Significant Difference ◽  
Average Flux

Abstract. Nitric oxide (NO) is a short-lived compound of the marine nitrogen cycle; however, our knowledge about its oceanic distribution and turnover is rudimentary. Here we present the measurements of dissolved NO in the surface and bottom layers at 75 stations in the Bohai Sea (BS) and the Yellow Sea (YS) in June 2011. Moreover, NO photoproduction rates were determined at 27 stations in both seas. The NO concentrations in the surface and bottom layers were highly variable and ranged from below the limit of detection (i.e., 32 pmol L−1) to 616 pmol L−1 in the surface layer and 482 pmol L−1 in the bottom layer. There was no significant difference (p>0.05) between the mean NO concentrations in the surface (186±108 pmol L−1) and bottom (174±123 pmol L−1) layers. A decreasing trend of NO in bottom-layer concentrations with salinity indicates a NO input by submarine groundwater discharge. NO in the surface layer was supersaturated at all stations during both day and night and therefore the BS and YS were a persistent source of NO to the atmosphere at the time of our measurements. The average flux was about 4.5×10-16 mol cm−2 s−1 and the flux showed significant positive relationship with the wind speed. The accumulation of NO during daytime was a result of photochemical production, and photoproduction rates were correlated to illuminance. The persistent nighttime NO supersaturation pointed to an unidentified NO dark production. NO sea-to-air flux densities were much lower than the NO photoproduction rates. Therefore, we conclude that the bulk of the NO produced in the mixed layer was rapidly consumed before its release to the atmosphere.

scholarly journals Characterization of Bacterial Communities in Bioaerosols over Northern Chinese Marginal Seas and the Northwestern Pacific Ocean in Spring

2019 ◽  
Vol 58 (4) ◽  
pp. 903-917 ◽  
Author(s):  
Manman Ma ◽  
Yu Zhen ◽  
Tiezhu Mi
Keyword(s):  
Pacific Ocean ◽  
Yellow Sea ◽  
Bacterial Communities ◽  
Bohai Sea ◽  
The Yellow Sea ◽  
Northwestern Pacific ◽  
Particle Sizes ◽  
Marine Aerosols ◽  
Northwestern Pacific Ocean ◽  
The Bohai Sea

AbstractStudies of the community structures of bacteria in marine aerosols of different particle sizes have not been reported. Aerosol samples were collected using a six-stage bioaerosol sampler over the Bohai Sea, the Yellow Sea, and northwestern Pacific Ocean in the spring of 2014. The diversity and composition of these samples were investigated by Illumina high-throughput sequencing, and 130 genera were detected in all of the samples; the most abundant bacterial genus was Bacteroides, followed by Prevotella and Megamonas. The Chao1 and Shannon diversity indices ranged from 193 to 1044 and from 5.44 to 8.33, respectively. The bacterial community structure in coarse particles (diameter larger than 2.1 μm) was more complex and diverse than that in fine particles (diameter less than 2.1 μm) in marine bioaerosols from over the Yellow Sea and northwestern Pacific Ocean, while the opposite trend was observed for samples collected over the Bohai Sea. Although we were sampling over marine regions, the sources of the bioaerosols were mostly continental. Temperature and wind speed significantly influenced the bacterial communities in marine aerosols of different particle sizes. There may be a bacterial background in the atmosphere in the form of several dominant taxa, and the bacterial communities are likely mixed constantly during transmission.

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